U.S. patent number 9,932,242 [Application Number 14/362,877] was granted by the patent office on 2018-04-03 for method for manufacturing cathode active material for lithium secondary battery.
This patent grant is currently assigned to SK Innovation Co., Ltd.. The grantee listed for this patent is SK Innovation Co., Ltd.. Invention is credited to Kook Hyun Han, Min Gu Kang, Seong Ho Lee, Jung In Yeon.
United States Patent |
9,932,242 |
Yeon , et al. |
April 3, 2018 |
**Please see images for:
( Certificate of Correction ) ** |
Method for manufacturing cathode active material for lithium
secondary battery
Abstract
Provided is a method for manufacturing a cathode active material
for a lithium secondary battery, the method including heat-treating
a precursor aqueous solution containing a lithium precursor, a
transition metal precursor, and an organic acid containing a
carboxyl group, and having a chelation index (C.I) value less than
1 and 0.5 or more, wherein the chelation index value is defined by
transmittance of a peak located in a wavenumber from 1,700 to 1,710
cm.sup.-1 and transmittance of a peak located in a wavenumber from
1,550 to 1,610 cm.sup.-1 in Fourier transform infrared (FTIR)
spectroscopy spectrum.
Inventors: |
Yeon; Jung In (Daejeon,
KR), Han; Kook Hyun (Daejeon, KR), Kang;
Min Gu (Seoul, KR), Lee; Seong Ho (Seoul,
KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
SK Innovation Co., Ltd. |
Seoul |
N/A |
KR |
|
|
Assignee: |
SK Innovation Co., Ltd. (Seoul,
KR)
|
Family
ID: |
48574593 |
Appl.
No.: |
14/362,877 |
Filed: |
December 6, 2012 |
PCT
Filed: |
December 06, 2012 |
PCT No.: |
PCT/KR2012/010544 |
371(c)(1),(2),(4) Date: |
June 04, 2014 |
PCT
Pub. No.: |
WO2013/085306 |
PCT
Pub. Date: |
June 13, 2013 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20140346392 A1 |
Nov 27, 2014 |
|
Foreign Application Priority Data
|
|
|
|
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Dec 6, 2011 [KR] |
|
|
10-2011-0129598 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M
4/505 (20130101); C01G 45/1242 (20130101); C01G
45/1228 (20130101); H01M 4/525 (20130101); C01G
53/50 (20130101); Y02E 60/10 (20130101); H01M
10/052 (20130101) |
Current International
Class: |
C01G
53/00 (20060101); H01M 4/505 (20100101); H01M
4/525 (20100101); C01G 45/12 (20060101); H01M
10/052 (20100101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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102496708 |
|
Jun 2012 |
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CN |
|
7142065 |
|
Jun 1995 |
|
JP |
|
950811 |
|
Feb 1997 |
|
JP |
|
1020090108964 |
|
Oct 2009 |
|
KR |
|
1020100060362 |
|
Jun 2010 |
|
KR |
|
1020100099594 |
|
Sep 2010 |
|
KR |
|
1020110039657 |
|
Apr 2011 |
|
KR |
|
1020110061204 |
|
Jun 2011 |
|
KR |
|
Other References
Julien C et al: "Layered LiNi0.5Co0.5O2 cathode materials grown by
soft-chemistry via various solution methods" Materials Science and
Engineering B, 2000, pp. 145-155, vol. 76, No. 2,Elsevier Sepuoia
Lausanne, Ch. cited by applicant .
Nam K W et al: "In situ X-ray diffraction studies of mixed
LiMn2O4-LiNi1/3Co1/3Mn1/3O2 composite cathode in Li-ion cells
during charge-discharge cycling", Journal of Power Sources, 2009,
pp. 652-659, vol. 192, No. 2, Elsevier SA, Ch. cited by
applicant.
|
Primary Examiner: Diggs; Tanisha
Attorney, Agent or Firm: The Webb Law Firm
Claims
The invention claimed is:
1. A method for manufacturing a cathode active material for a
lithium secondary battery, comprising: gelling a precursor aqueous
solution containing a lithium precursor, a transition metal
precursor, and an organic acid containing a carboxyl group to
prepare a precursor gel having Fourier transform infrared (FTIR)
spectroscopy spectrum satisfying the following Equation 2 by the
definition of the following Equation 1, and heat-treating the
precursor gel:
.times..times..times..times..times..times..function..times..times..times.-
.times..times..function..times..times. ##EQU00003##
0.640.ltoreq.C.I..ltoreq.0.763 (Equation 2) wherein in Equation 1
above, % Transmittance (1700) means transmittance of a peak located
at a wavenumber from 1,700 to 1,710 cm.sup.-1 in FTIR spectrum of
the precursor gel and % Transmittance (1550) means transmittance of
a peak located at a wavenumber from 1,550 to 1,610 cm.sup.-1 in the
same FTIR spectrum, wherein gelling the precursor aqueous solution
is performed at 60 to 90.degree. C. under a pressure of 100 mbar to
300 mbar.
2. The method of claim 1, wherein the transition metal precursor is
a precursor of one or two or more metals selected from a group
consisting of nickel, cobalt, manganese, aluminum, magnesium,
chromium, iron, zirconium, titanium, zinc, scandium, yttrium,
niobium, molybdenum and ruthenium.
3. The method of claim 1, wherein the lithium precursor and the
transition metal precursor are each independently nitrates,
acetates, hydroxides, chlorides, sulfur oxides, or mixtures
thereof.
4. The method of claim 1, wherein the precursor aqueous solution
contains the lithium precursor and the transition metal precursor
so as to satisfy the following Equation 3 or 4:
Li.sub.1+xNi.sub..alpha.Mn.sub..beta.Co.sub..gamma.M'.sub..delta.O.sub.2
(Equation 3) LiMn.sub.2-yM''.sub.yO.sub.4 (Equation 4) wherein in
Equation 3 above, x is an actual number satisfying
-0.04.ltoreq.x<1, .alpha., .beta., .gamma., and .delta. are
actual numbers satisfying .alpha.+.beta.+.gamma.+.delta.=1 and
0.ltoreq..alpha.<1, 0.ltoreq..beta.<1, 0.ltoreq..gamma.<1,
and 0.ltoreq..delta.<1, and M' is one or more metals selected
from aluminum, magnesium, chromium, iron, zirconium, titanium,
zinc, scandium, yttrium, niobium, molybdenum and ruthenium, and
wherein in Equation 4 above, y is an actual number satisfying
0.ltoreq.y<2 and M'' is one or more metals selected from nickel,
cobalt, aluminum, magnesium, chromium, iron, zirconium, titanium,
zinc, scandium, yttrium, niobium, molybdenum and ruthenium.
5. The method of claim 4, wherein the precursor aqueous solution
has a molar concentration of lithium ions of 0.1M to 7.0M.
6. The method of claim 1, wherein the heat-treating is performed at
200 to 1000.degree. C.
7. The method of claim 6, wherein the heat-treating is a spray
pyrolysis process.
8. The method of claim 2, wherein the heat-treating is performed at
200 to 1000.degree. C.
9. The method of claim 3, wherein the heat-treating is performed at
200 to 1000.degree. C.
10. The method of claim 4, wherein the heat-treating is performed
at 200 to 1000.degree. C.
11. The method of claim 5, wherein the heat-treating is performed
at 200 to 1000.degree. C.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is the United States national phase of
International Application No. PCT/KR2012/01054 filed Dec. 6, 2012,
and claims priority to Korean Patent Application No.
10-2011-0129598 filed Dec. 6, 2011, the disclosures of which are
hereby incorporated in their entirety by reference.
TECHNICAL FIELD
The present invention relates to a method for manufacturing a
cathode active material for a lithium secondary battery, and more
particularly, to a method for manufacturing a cathode active
material capable of having uniform composition and easily inserting
lithium ions thereinto and easily desorbing lithium ions
therefrom.
BACKGROUND ART
A battery is largely classified into primary and secondary
batteries, wherein the primary battery, which is a battery of
producing electricity by a non-reversible reaction to be
non-reusable after the battery is used once, includes a dry battery
generally used, a mercury battery, a Volta's battery, and the like,
by way of an example; meanwhile, the secondary battery, which is a
battery of using a reversible reaction to be reusable by charging
after being used, unlike the primary battery, includes a lead
storage battery, a lithium ion battery, a nickel-cadmium (Ni--Cd)
battery, and the like, by way of an example.
The lithium ion battery, which is one of the secondary battery, is
configured to include an anode generally consisting of carbon, a
cathode generally consisting of lithium compounds, an electrolyte
disposed between the anode and the cathode, and a wire connecting
the anode and the cathode. Lithium ions in the electrolyte moves
toward the anode at the time of charging, and moves toward the
cathode at the time of discharging, and generate a chemical
reaction while discharging surplus electrons from each pole or
absorbing surplus electrons thereinto. During this process,
electrons flow in the wire, and thus, an electric energy is
generated.
Life, energy density, and thermal stability of the lithium
secondary battery are mainly determined by the cathode active
material. It is known that physical properties of the cathode
active material are largely affected by composition of the active
material and a method for manufacturing the same.
As a general method for manufacturing the cathode active material,
Korean Patent Laid-Open Publication No. 2009-0108964 discloses a
solid phase reaction method and Korean Patent Laid-Open Publication
No. 2011-0039657 discloses a coprecipitation method. The solid
phase reaction method is a method for manufacturing a cathode
active material by using carbonate or hydroxide of each element
constituting the cathode active material and repeating mixing and
heat-treating processes several times, and the coprecipitation
method is a method for manufacturing a cathode active material by
mixing a precursor with a lithium source, and then performing a
heat-treatment, wherein the precursor is prepared by mixing each
element constituting the cathode active material except for lithium
in a solution, followed by coprecipitation.
However, in the solid phase method, there is a risk in that
impurities flow in mixing solid phase raw materials, and since the
cathode active materials are manufactured by solid phase diffusion,
there is a difficulty in manufacturing a phase having uniform
composition and in adjusting a size of final particles, and at the
time of manufacturing, energy and time are significantly consumed.
In the coprecipitation method, precise control in processes is
required to obtain uniform precipitation, pollution caused by
additives for precipitation is inevitable, a large amount of waste
liquid occurs. In addition, as compared to the solid phase method,
the active material manufactured by the coprecipitation method has
uniform composition; however, there is still compositional
non-uniformity.
Therefore, development of a method for manufacturing a cathode
active material having significantly excellent compositional
uniformity and high capacity, being free of pollution, and being
manufactured by mass-production with a simple process, a
short-time, and a low cost, in an environment-friendly manner in
which by-products such as waste liquid do not occur, has been
urgently demanded.
DISCLOSURE
Technical Problem
An object of the present invention is to provide a precursor
aqueous solution capable of manufacturing a cathode active material
having excellent compositional uniformity and easily inserting
lithium ions thereinto and easily desorbing lithium ions therefrom
at the time of manufacturing the cathode active material for a
lithium secondary battery, and a method for manufacturing the
cathode active material for a lithium secondary battery using the
same.
Technical Solution
In one general aspect, the present invention provides a method for
manufacturing a cathode active material for a lithium secondary
battery, including: heat-treating a precursor aqueous solution
containing a lithium precursor, a transition metal precursor, and
an organic acid containing a carboxyl group, and having Fourier
transform infrared (FTIR) spectroscopy spectrum satisfying the
following Equation 2 by the definition of the following Equation
1:
.times..times..times..times..times..times..function..times..times..times.-
.times..times..function..times..times. ##EQU00001##
0.5.ltoreq.C.I.<1 (Equation 2)
(in Equation 1 above, % Transmittance (1700) means transmittance of
a peak located at a wavenumber from 1,700 to 1,710 cm.sup.-1 in
FTIR spectrum of a precursor gel obtained by preparing the
precursor aqueous solution as a gel, and % Transmittance (1550)
means transmittance of a peak located at a wavenumber from 1,550 to
1,610 cm.sup.-1 in the same FTIR spectrum).
The transition metal precursor may be a precursor of one or two or
more metals selected from a group consisting of nickel, cobalt,
manganese, aluminum, magnesium, chromium, iron, zirconium,
titanium, zinc, scandium, yttrium, niobium, molybdenum and
ruthenium.
The lithium precursor and the transition metal precursor may be
each independently nitrates, acetates, hydroxides, chlorides,
sulfur oxides, or mixtures thereof.
The precursor aqueous solution may contain the lithium precursor
and the transition metal precursor so as to satisfy the following
Equation 3 or 4:
Li.sub.1+xNi.sub..alpha.Mn.sub..beta.Co.sub..gamma.M'.sub..delta.O.sub-
.2 (Equation 3)
(in Equation 3 above, x is an actual number satisfying
-0.04.ltoreq.x<1, .alpha., .beta., .gamma., and .delta. are
actual numbers satisfying .alpha.+.beta.+.gamma.+.delta.=1 and
0.ltoreq..alpha.<1, 0.ltoreq..beta.<1, 0.ltoreq..gamma.<1,
and 0.ltoreq..delta.<1, and M' is one or more metals selected
from aluminum, magnesium, chromium, iron, zirconium, titanium,
zinc, scandium, yttrium, niobium, molybdenum and ruthenium)
LiMn.sub.2-yM''.sub.yO.sub.4 (Equation 4)
(in Equation 4 above, y is an actual number satisfying
0.ltoreq.y<2 and M'' is one or more metals selected from nickel,
cobalt, aluminum, magnesium, chromium, iron, zirconium, titanium,
zinc, scandium, yttrium, niobium, molybdenum and ruthenium).
The precursor aqueous solution may have a molar concentration of
lithium ions of 0.1M to 7.0M.
The method may further include: preparing the precursor aqueous
solution as a gel.
The heat-treating may be a spray pyrolysis process.
In another general aspect, the present invention provides a cathode
active material for a lithium secondary battery satisfying the
following Equation 3 or the following Equation 4, and having a
hexagonal compact structure in which a lattice constant ratio (c/a)
is 4.975 or more:
Li.sub.1+xNi.sub..alpha.Mn.sub..beta.Co.sub..gamma.M'.sub..delta.O.sub.2
(Equation 3)
(in Equation 3 above, x is an actual number satisfying
-0.04.ltoreq.x<1, .alpha., .beta., .gamma., and .delta. are
actual numbers satisfying .alpha.+.beta.+.gamma.+.delta.=1 and
0.ltoreq..alpha.<1, 0.ltoreq..beta.<1, 0.ltoreq..gamma.<1,
and 0.ltoreq..delta.<1, and M' is one or more metals selected
from aluminum, magnesium, chromium, iron, zirconium, titanium,
zinc, scandium, yttrium, niobium, molybdenum and ruthenium)
LiMn.sub.2-yM''.sub.yO.sub.4 (Equation 4)
(in Equation 4 above, y is an actual number satisfying
0.ltoreq.y<2 and M'' is one or more metals selected from nickel,
cobalt, aluminum, magnesium, chromium, iron, zirconium, titanium,
zinc, scandium, yttrium, niobium, molybdenum and ruthenium).
Advantageous Effects
The precursor aqueous solution according to the present invention
uses an organic acid containing a carboxylic group which is a
chelating agent, such that the lithium and the transition metal are
mixed with each other in a water-based solution, and the Equation 2
above is satisfied according to the Equation 1 above, such that the
lithium and the transition metal may have uniformity maintained
even at the time of water evaporation, decomposition and removal of
organic materials, and nucleation and growth of the active
material, thereby manufacturing the cathode active material having
excellent crystallinity and significant uniform composition, and
easily inserting lithium ions thereinto and easily desorbing
lithium ions therefrom.
DESCRIPTION OF DRAWINGS
FIG. 1 shows results obtained by measuring precursor gels
manufactured in Manufacturing Examples 1 and 2, and Comparative
Examples 1 and 2, by Fourier transform infrared (FTIR)
spectroscopy;
FIG. 2 shows results obtained by measuring each lattice constant
ratio (c/a) of cathode active materials manufactured in
Manufacturing Examples 3 and 4, and Comparative Examples 3 and
4;
FIG. 3 shows charge and discharge properties of each unit cell
manufactured in Manufacturing Examples 5 and Comparative Examples
6, 7, and 8; and
FIG. 4 shows relationships between capacity and lattice constant
ratio of each unit cell manufactured in Manufacturing Examples 5
and 6 and Comparative Examples 6 and 7.
BEST MODE
Hereinafter, a method for manufacturing a cathode active material
according to the present invention will be described. Here, unless
technical and scientific terms used herein are defined otherwise,
they have meanings understood by those skilled in the art to which
the present invention pertains. Known functions and components
which obscure the description and the accompanying drawings of the
present invention with unnecessary detail will be omitted.
As a result of research on a cathode active material for a lithium
secondary battery, the present inventors found that at the time of
manufacturing the cathode active material, a cathode active
material having uniformity and excellent capacity is manufactured
by mixing lithium with transition metal in a precursor aqueous
solution and at the time of preparing the precursor aqueous
solution as a gel, adding a chelating agent into the aqueous
solution so as to satisfy specific conditions, thereby completing
the present invention.
The method for manufacturing a cathode active material for a
lithium secondary battery, according to an exemplary embodiment of
the present invention includes: heat-treating a precursor aqueous
solution containing a lithium precursor, a transition metal
precursor, and an organic acid containing a carboxyl group, and
having Fourier transform infrared (FTIR) spectroscopy spectrum
satisfying the following Equation 2 by the definition of the
following Equation 1:
.times..times..times..times..times..times..function..times..times..times.-
.times..times..function..times..times. ##EQU00002##
0.5.ltoreq.C.I.<1 (Equation 2)
(in Equation 1 above, % Transmittance (1700) means transmittance of
a peak located at a wavenumber from 1,700 to 1,710 cm.sup.-1 in
FTIR spectrum of a precursor gel obtained by preparing the
precursor aqueous solution as a gel, and % Transmittance (1550)
means transmittance of a peak located at a wavenumber from 1,550 to
1,610 cm.sup.-1 in the same FTIR spectrum).
In detail, the precursor gel which is a measurement target of FTIR
spectrum may include a gel obtained by reacting the precursor
aqueous solution containing a lithium precursor, a transition metal
precursor, and an organic acid containing a carboxyl group under a
pressure of 153 mbar and at a temperature of 75.degree. C. for 2
hours, by a vacuum evaporator.
In detail, the FTIR spectrum of the precursor gel may include a
FTIR spectrum obtained under resolution measurement condition of 4
cm.sup.-1 in 500-4000 cm.sup.-1 region which is a Mid-IR
region.
More specifically, the FTIR spectrum may include a spectrum having
a wavenumber of an infrared light to be irradiated as one axis and
transmittance according to a wavenumber of light as the other axis,
wherein when light to be irradiated, having a specific wavenumber
is all transmitted, transmittance of the other axis may include %
transmittance having 100% of transmittance, and a peak on the FTIR
spectrum may include a peak toward a direction in which
transmittance is reduced.
In detail, the peak at located from 1700 to 1710 cm.sup.-1 may
include a peak according to a carboxylic group, and the peak at
located from 1550 to 1610 cm.sup.-1 may include a peak according to
a carboxylate formed by chelation with metal ions.
The method for manufacturing the cathode active material according
to an exemplary embodiment of the present invention uses the
precursor aqueous solution containing a lithium precursor, a
transition metal precursor, and an organic acid containing a
carboxyl group, and satisfying the Equation 2 by the definition of
the Equation 1, such that lithium and a transition metal are
uniformly chelated, thereby manufacturing the cathode active
material in which the lithium and the transition metal are
significantly and uniformly coupled to each other and lithium ions
are easily inserted into the cathode active material and easily
desorbed from the cathode active material.
In detail, the precursor aqueous solution satisfies the Equation 2
by the definition of Equation 1, such that the cathode active
material being uniform and having excellent crystallinity and
excellent charge and discharge properties may be manufactured by a
heat-treatment of the precursor aqueous solution.
In the method for manufacturing the cathode active material
according to an exemplary embodiment of the present invention, an
organic acid containing a carboxylic group which is a chelating
agent is used, such that the lithium and the transition metal are
mixed with each other in a water-based solution, and the Equation 2
is satisfied according to the Equation 1, such that at the time of
heat-treatment, the lithium and the transition metal may have
uniformity maintained even at the time of nucleation and growth of
the desired lithium composite metal oxide, thereby manufacturing a
cathode active material having excellent crystallinity and
significant uniform composition, and easily inserting lithium ions
thereinto and easily desorbing lithium ions therefrom.
The method for manufacturing a cathode active material according to
an exemplary embodiment of the present invention may further
include preparing the above-described precursor aqueous solution as
a gel. The preparing of the precursor aqueous solution as a gel may
be performed by reaction under a pressure of 100 mbar to 300 mar
and at a temperature of 60 to 90.degree. C. for 1 to 3 hours.
It does not matter that the cathode active material is manufactured
by heat-treating the precursor aqueous solution itself satisfying
the above-described Equations 1 and 2. However, the cathode active
material may be manufactured by preparing an aqueous solution as a
gel and then heat-treating the precursor gel. When using the
precursor gel, an output of the cathode active material may be
increased in a significantly short time.
As described above, at the time of heat-treating the precursor
aqueous solution satisfying the Equations 1 and 2 or the precursor
gel obtained by preparing the precursor aqueous solution satisfying
the Equations 1 and 2 as a gel, significantly uniform composition
thereof is maintained at the time of nucleation and growth of the
cathode active material, thereby manufacturing the cathode active
material having excellent crystallinity and uniform composition
without forming a different phase.
In detail, the FTIR properties have a significant effect on
crystallinity and uniformity of a cathode active material to be
manufactured, and the precursor aqueous solution according to the
present invention satisfies the Equation 2 above according to the
Equation 1 above, such that a lithium composite metal oxide
(cathode active material) having a hexagonal compact structure in
which a lattice constant ratio (c/a) is 4.975 or more may be
manufactured.
When the precursor aqueous solution does not satisfy the Equation 2
above, a lithium composite metal oxide in which the ratio of c/a is
less than 4.975, is merely manufactured, and compositional
uniformity of the lithium composite metal oxide particles to be
manufactured may not be secured, and the undesired different phase
may be formed.
That is, the method for manufacturing the cathode active material
according to an exemplary embodiment of the present invention uses
the precursor aqueous solution satisfying the Equations 1 and 2,
such that compositional uniformity according to removal of water
and/or organic materials is not deteriorated, thereby manufacturing
a high qualified cathode active material having uniform composition
and excellent crystallinity.
In the method for manufacturing the cathode active material
according to an exemplary embodiment of the present invention, the
heat-treatment for manufacturing the cathode active material may be
performed at 200 to 1000.degree. C. and under an atmosphere
containing oxygen. In detail, the heat-treatment may be a multiple
heat-treatment including a low temperature heat-treatment at 200 to
400.degree. C. and a high temperature heat-treatment at 600 to
1000.degree. C., wherein the low temperature heat-treatment may be
performed for 1 to 4 hours and then the high temperature
heat-treatment may be continuously and non-continuously performed
for 15 to 25 hours. By the above-described multiple heat-treatment,
crystallinity of the cathode active material, together with the
precursor aqueous solution satisfying the Equations 1 and 2, may be
improved.
In the method for manufacturing the cathode active material
according to an exemplary embodiment of the present invention, the
heat-treatment for manufacturing the cathode active material may be
a spray pyrolysis process. The uniformity of the precursor aqueous
solution (or the precursor gel) which is a heat-treatment target is
obtained since the precursor aqueous solution contains an organic
acid containing a carboxylic group so as to satisfy the
above-described Equations 1 and 2, wherein the uniformity is stably
maintained, such that the cathode active material may be
manufactured by a spray pyrolysis process.
The spray pyrolysis process, which is a method in which production
of droplet (droplet of the precursor aqueous solution), dryness,
and nucleation and growth of the desired lithium composite metal
oxide are performed in a significantly short time, is appropriate
for mass-production of particles of a spherical shaped fine cathode
active material (lithium composite metal oxide); however, has
disadvantages in that the cathode active material to be
manufactured has deteriorated crystallinity and excessively
compositional non-uniformity.
However, according to an exemplary embodiment of the present
invention, the precursor aqueous solution (or precursor gel)
satisfying the above-described Equations 1 and is used, such that
the cathode active material having excellent crystallinity and
compositional uniformity may be manufactured while using a spray
pyrolysis process which is appropriate for mass-production.
At the time of the spray pyrolysis process, the droplet may have an
average size of 0.1 to 100 .mu.m and may be pyrolyzed
(heat-treated) at a temperature of 400 to 1000.degree. C. The
average size of the droplet is a size in which a spherical shaped
lithium composite metal oxide (cathode active material) powder is
capable of being obtained and excellent tab density may be
obtained, and the pyrolysis temperature is a condition in that the
lithium composite metal oxide is stably manufactured in a
short-time, and densified lithium composite metal oxide particles
are capable of being manufactured.
A transfer gas transferring the produced droplet to an ultrasonic
vibrator or a nozzle contains oxygen, for example, oxygen or an
inert gas containing air or oxygen, may be used.
The transfer gas may have a flow velocity of 1 to 500 L/min. The
flow velocity of the transfer gas is a flow velocity at which the
cathode active material having uniform composition and densified
spherical particles is capable of being manufactured in a
significantly short time of several to dozens of seconds in the
pyrolysis (heat-treatment) process.
Optionally, the cathode active material particles obtained by the
spray pyrolysis process may be subjected to a post-treatment which
is a heat-treatment at a temperature of 600 to 1000.degree. C. for
20 minutes to 20 hours. By the post-treatment, a cathode active
material having significantly excellent crystallinity and uniform
composition may be manufactured.
In the method for manufacturing the cathode active material
according to an exemplary embodiment of the present invention, the
lithium precursor contained in the precursor aqueous solution may
be any lithium precursor as long as the lithium precursor is
capable of being dissolved in water, and may substantially include
nitrate, acetate, hydroxide, chloride, sulphate of lithium, or
mixtures thereof.
In the method for manufacturing the cathode active material
according to an exemplary embodiment of the present invention, the
organic acid containing a carboxylic group contained in the
precursor aqueous solution may be any organic acid as long as the
organic acid is capable of being dissolved in water and contains a
carboxylic group, and may include a malic acid, a citric acid, a
succinic acid, an oxalic acid, tartrate, an acrylic acid, a humic
acid, an ascorbic acid, or mixtures thereof.
In the method for manufacturing the cathode active material
according to an exemplary embodiment of the present invention, the
transition metal precursor contained in the precursor aqueous
solution may include a precursor of one or two or more metals
selected from a group consisting of nickel, cobalt, manganese,
aluminum, magnesium, chromium, iron, zirconium, titanium, zinc,
scandium, yttrium, niobium, molybdenum and ruthenium.
In the method for manufacturing the cathode active material
according to an exemplary embodiment of the present invention, the
transition metal precursor contained in the precursor aqueous
solution may be any transition metal precursor as long as the
transition metal precursor is capable of being dissolved in water,
and may include nitrate, acetate, hydroxide, chloride, sulphate of
the transition metal, or mixtures thereof, as being independently
of the lithium precursor.
In the method for manufacturing the cathode active material
according to an exemplary embodiment of the present invention, the
precursor aqueous solution may contain the lithium precursor and
the transition metal precursor so as to satisfy the following
Equation 3 or 4:
Li.sub.1+xNi.sub..alpha.Mn.sub..beta.Co.sub..gamma.M'.sub..delta.O.sub.2
(Equation 3)
(in Equation 3 above, x is an actual number satisfying
-0.04.ltoreq.x<1, .alpha., .beta., .gamma., and .delta. are
actual numbers satisfying .alpha.+.beta.+.gamma.+.delta.=1 and
0.ltoreq..alpha.<1, 0.ltoreq..beta.<1, 0.ltoreq..gamma.<1,
and 0.ltoreq..delta.<1, and M' is one or more metals selected
from aluminum, magnesium, chromium, iron, zirconium, titanium,
zinc, scandium, yttrium, niobium, molybdenum and ruthenium)
LiMn.sub.2-yM''.sub.yO4 (Equation 4)
(in Equation 4 above, y is an actual number satisfying
0.ltoreq.y<2 and M'' is one or more metals selected from nickel,
cobalt, aluminum, magnesium, chromium, iron, zirconium, titanium,
zinc, scandium, yttrium, niobium, molybdenum and ruthenium).
In the method for manufacturing the cathode active material
according to an exemplary embodiment of the present invention, a
molar concentration of lithium ions contained in the precursor
aqueous solution may be 0.1M to 7.0M, and the precursor aqueous
solution may contain a precursor of one or two or more metals
selected from nickel, cobalt, manganese, aluminum, magnesium,
chromium, iron, zirconium, titanium, zinc, scandium, yttrium,
niobium, molybdenum and ruthenium, so as to satisfy a relative
ratio of lithium ions according to the Equation 3 or 4, together
with the lithium precursor satisfying the molar concentration of
lithium ions.
In the method for manufacturing the cathode active material
according to an exemplary embodiment of the present invention, by
using the above-described precursor aqueous solution, the cathode
active material in which the mass-production is possible at a low
const and high crystallinity and high capacity are provided by a
simple heat-treatment, may be manufactured, and the high qualified
cathode active material may be manufactured by the spray pyrolysis
method which is appropriate for mass-production.
The present invention contains a cathode active material for a
lithium secondary battery. The cathode active material according to
an exemplary embodiment of the present invention may be a lithium
composite metal oxide satisfying the following Equation 3 or 4 and
may be a lithium composite metal oxide having a hexagonal compact
structure in which a lattice constant ratio (c/a) is 4.975 or more.
By heat-treating the above-described precursor aqueous solution,
the cathode active material according to an exemplary embodiment of
the present invention may have a hexagonal compact structure in
which a lattice constant ratio (c/a) is 4.975 or more, and thus,
lithium ions may be easily inserted into the cathode active
material or easily desorbed from the cathode active material.
Li.sub.1+xNi.sub..alpha.Mn.sub..beta.Co.sub..gamma.M'.sub..delt-
a.O.sub.2 (Equation 3)
(in Equation 3 above, x is an actual number satisfying
-0.04.ltoreq.x<1, .alpha., .beta., .gamma., and .delta. are
actual numbers satisfying .alpha.+.beta.+.gamma.+.delta.=1 and
0.ltoreq..alpha.<1, 0.ltoreq..beta.<1, 0.ltoreq..gamma.<1,
and 0.ltoreq..delta.<1, and M' is one or more metals selected
from aluminum, magnesium, chromium, iron, zirconium, titanium,
zinc, scandium, yttrium, niobium, molybdenum and ruthenium)
LiMn.sub.2-yM''.sub.yO4 (Equation 4)
(in Equation 4 above, y is an actual number satisfying
0.ltoreq.y<2 and M'' is one or more metals selected from nickel,
cobalt, aluminum, magnesium, chromium, iron, zirconium, titanium,
zinc, scandium, yttrium, niobium, molybdenum and ruthenium).
Hereinafter, the following Manufacturing Examples of the present
invention will be described in detail. However, the Manufacturing
Examples are described by way of examples only, and thus, it is not
construed to limit the appended claims thereto.
Manufacturing Example 1
A precursor aqueous solution was prepared by dissolving lithium
nitrate, nickel nitrate, manganese nitrate, and cobalt nitrate in a
distilled water so as to satisfy composition of
LiNi.sub.0.33Mn.sub.0.33Co.sub.0.33O.sub.2, and adding a citric
acid thereto so as to satisfy C.I.=0.763 like the result of FTIR
shown in `Manufacturing Example 1` of FIG. 1 at the time of
gelation. The gelation was performed by reacting the prepared
precursor aqueous solution under a pressure of 153 mbar and at a
temperature of 75.degree. C. for 2 hours, by a vacuum evaporator.
The FTIR measurement was conducted by Nicolet 6700 FTIR System and
SMART Orbit ATR Accessory (ZnSe) supplied by Thermo Fisher
Scientific company, under resolution measurement condition of 4
cm.sup.-1 in 500-4000 cm.sup.-1 region which is a Mid-IR
region.
Manufacturing Example 2
A precursor aqueous solution was prepared by the same manner as the
Manufacturing Example 1 above, except for adding a citric acid
thereto so as to satisfy C.I.=0.640 like the result of FTIR of the
precursor gel shown in `Manufacturing Example 2` of FIG. 1 at the
time of gelation which was the same as Manufacturing Example 1.
Comparative Example 1
A precursor aqueous solution was prepared by the same manner as the
Manufacturing Example 1 above, except for adding a citric acid
thereto so as to satisfy C.I.=0.451 like the result of FTIR of the
precursor gel shown in `Comparative Example 1` of FIG. 1 at the
time of gelation which was the same as Manufacturing Example 1.
Comparative Example 2
A precursor aqueous solution was prepared by the same manner as the
Manufacturing Example 1 above, except for not adding a citric acid
thereto, and the measurement result of FTIR of the precursor gel
obtained by the same gelation as the Manufacturing Example 1 was
shown as `Comparative Example 2` in FIG. 1.
Manufacturing Example 3
A cathode active material having a composition of
LiNi.sub.0.33Mn.sub.0.33Co.sub.0.33O.sub.2 was manufactured by
heat-treating the precursor gel prepared by the Manufacturing
Example 1 above in the air at 300.degree. C. for 2 hours, and
heat-treating again at an atmosphere into which air of 2 L/min is
injected, at 900.degree. C. for 20 hours.
Manufacturing Example 4
A cathode active material was manufactured by the same manner as
the Manufacturing Example 3 above, except for using the precursor
gel manufactured by the Manufacturing Example 2 above.
Comparative Example 3
A cathode active material was manufactured by the same manner as
the Manufacturing Example 3 above, except for using the precursor
gel manufactured by the Comparative Example 1 above.
Comparative Example 4
A cathode active material was manufactured by the same manner as
the Manufacturing Example 3 above, except for using the precursor
gel manufactured by the Comparative Example 2 above.
Comparative Example 5
A cathode active material having a composition of
LiNi.sub.0.33Mn.sub.0.33Co.sub.0.33O.sub.2 was manufactured by a
coprecipitation method.
Manufacturing Example 5
Cathode was manufactured by coating a slurry containing the cathode
active material manufactured by the Manufacturing Example 3 above
onto a current collector made of an aluminum foil, followed by
drying and rolling processes, so as to have a density of 1.9 to 2.1
g/cm.sup.2, and the manufactured cathode (12.PHI.), separator
(16.4.PHI.), lithium metal anode (16.2.PHI.) were stacked to each
other, thereby manufacturing a unit cell.
Manufacturing Example 6
A unit cell was manufactured by the same manner as the
Manufacturing Example 5 above, except for using the cathode active
material manufactured by the Manufacturing Example 4 above.
Comparative Example 6
A unit cell was manufactured by the same manner as the
Manufacturing Example 5 above, except for using the cathode active
material manufactured by the Comparative Example 3 above.
Comparative Example 7
A unit cell was manufactured by the same manner as the
Manufacturing Example 5 above, except for using the cathode active
material manufactured by the Comparative Example 4 above.
Comparative Example 8
A unit cell was manufactured by the same manner as the
Manufacturing Example 5 above, except for using the cathode active
material manufactured by the Comparative Example 5 above.
FIG. 2 shows a result obtained by measuring lattice constants (a
and c) of the cathode active materials manufactured by the
Manufacturing Examples 3 and 4, and Comparative Examples 3 and 4.
It was confirmed from FIG. 2 that when manufacturing the cathode
active material using the precursor aqueous solution according to
the present invention, the cathode active material having a
hexagonal compact structure in which a lattice constant ratio (c/a)
is 4.975 or more was manufactured.
FIG. 3 shows a result obtained by measuring electric properties of
the unit cells manufactured by the Manufacturing Examples 5 and 6,
and Comparative Examples 6, 7, and 8, which is obtained under
conditions including charging up to 4.3V with a ratio of 0.1C while
assuming that a reversible capacity is 180 mAh/g, and the
discharging up to 3V with the same ratio. It could be appreciated
from FIG. 3 that when manufacturing the cathode active material
using the precursor aqueous solution according to the present
invention, an initial discharge capacity of 168 mAh/g and 167 mAh/g
was obtained, and excellent performance was provided.
FIG. 4 shows battery capacity and the c/a ratio of the cathode
active material, of the Manufacturing Examples 5 and 6 and
Comparative Examples 6 and 7, and it could be appreciated from FIG.
4 that as the cathode active material manufactured by the precursor
aqueous solution according to the present invention has high c/a
ratio, the discharge capacity was also high.
* * * * *